Is a 9mm Carbine less "loud" than a pistol?

[Orion8472]

Thanks!

 

[shoobe01]

Strongly agree that distance-from-head is a much bigger deal than barrel length. Try retention position with the handgun and see how unpleasant that is compared to normal firing position.

Not handguns, but pretty recently I got a .308 bullpup. Same barrel length as other things I've got and it is loud to jarringly so (like, under cover) without the suppressor, for the one closer to my head.

Also plenty of people shoot pistol carbines at the IDPA club, and sometimes police bring their subguns even. Observing, pistols, subgun/SBR and 16" carbines in the same caliber sound +/- the same. If anything is louder, it's a carbine with a brake or someone shooting more powerful ammo from the carbine.

 

[Leon tP]

...
You can find pressure curves that show definitively that the pressure drops as the bullet moves down the barrel.

There are several at this website.
https://www.frfrogspad.com/intballi.htm

There's an initial peak that happens very early in bullet travel, then from there on, the pressure drops continually until the bullet exits.

However, even though it is lower by the time the bullet exits from the barrel, it is still significant enough that the push it creates on the back of the bullet is also significant. Even though it's dropping as the bullet moves down the barrel, it's still exerting enough force to keep accelerating the bullet.

From one of the pressure plots on the linked website, it can be seen that the chamber pressure in that particular case is still over 10,000psi at bullet exit. That's still going to be pushing on the bullet with a lot of force, even if it's not as much force as it was earlier.

Think of as pushing a heavy cart. At the beginning, you have to push very hard, then as it gets rolling, you can stop pushing quite as hard, but even so, you can keep it speeding up even by pushing with less force than you used at the beginning to get it started. The longer you push, the faster it goes, even if you're not pushing as hard at the end as you were at the beginning.

Thanks JohnKSa for that moment of clarity. I appreciate it.

 

[Boomholzer]

There is less "bang" or sound pressure envelope, to use nerdy words, perceived by the operator for a few reasons previous posters addressed. Gas velocity at the muzzle is reduced as a factor of reduced gas temperature as more work is imparted in pushing the bullet's velocity to the muzzle. Think about it just using the conservation of energy law. A very simple law that allows direction on complex dynamic problems or questions.
Relative to barrel length; unburnt propellant or powder along for the ride is introduced to a less pressure environment in our atmosphere to burn and contribute to the bang or shockwave. Distance from muzzle to operator is a factor and while not always pistol specific; direction of the gasses is a factor. Like being on the rifle firing line trying to score next to a tank brake that changes your hair part.

Reverting back to the physics part. A suppressor is a automotive muffler and nothing magical. Its a bit of a filter. It takes gas velocity past the muzzle and baffles it turning it into heat (again conservation of energy). The bullet is allowed to pass uninhibited through the baffles and more often is slightly accelerated (15fps in my 22" 30's) as the efficiency of a suppressor relative to sound suppression is not perfect. There is still enough gas velocity to push the projectile or bullet. A suppressor will get more "free boost" from shorter barrels. I haven't spent any time chronographing 9mm carbines but its fair to say the bullet leaves faster then a pistol. It does in 357, 44 and 45LC I measured so I am making some generalizations I believe to be true. This is again relative to gas temp and velocity that pokes our ears.

Is a 9mm carbine sufficiently quiet to ignore ear protection? Obviously no. Its a interesting discussion but a bit of moot point. Another factor in pistol carbines and perceived noise is action timing. Direct blowback auto loaders will open the action earlier then a cam'ed or locked breech auto pistol. IMO 9mm suppressors on these animals (like a 18" Ruger PC Carbine that was mentioned) even with subsonic bullet velocities is disappointing. With that observation, just focusing for "bang" at the muzzle isn't the whole story.

 

[bullseye308]

I have an AR-9 with an 8” barrel on it and a few pistols with 4.5-5” barrels on them. I added a linear comp to the AR and it is noticeably different. I didn’t notice much difference before the linear comp, but everyone likes it better now. Maybe look into one for yours and see for yourself then decide.

 

[DoubleMag]

Excellent FIRST POST AWARD goes to ...

Boomholzer ^^

WELCOME to THR

 

[Bfh_auto]

Excellent FIRST POST AWARD goes to ...

Boomholzer ^^

WELCOME to THR

That's about 5 posts worth of good information in one.

 

[denton]

JohnKsa has it right.

As long as your bullet is subsonic, the sound level is completely determined by the pressure of the propellant at the time the bullet exits. QuikLoad will calculate that for you. Using numbers from my usual 9mm load, it calculates that muzzle pressure at bullet exit in a 5" barrel is 3727 PSI. Changing the barrel to 16" reduces exit pressure to 1034 PSI.

The source I checked says that the sound pressure level is directly proportional to the pressure at exit. So in this case, the carbine would have about 1/4 the sound pressure level of the handgun, which is close to the 6dB mentioned earlier.

Since your ear responds logarithmically, you wouldn't perceive it as a 1/4 as loud. 3dB is about the smallest change that most people will notice. So at 6dB, the difference is easily noticed.

 

[chicharrones]

Not discounting all the other factors at play here, but when I "snuggle" up to my Beretta CX4 (9mm) with a 16.6" barrel, the muzzle is only about 5" further away than when I hold a 4" barreled 9mm pistol in an isosceles shooting stance.

The other interesting fact is that the longer barreled Beretta's breech is much closer to my ears when in a firing position than a pistol's breech is when held at arms length. That might not mean much in a manually operated gun, but in autoloaders . . .

Of course, a CX4 is a shorter gun than a Ruger PCC, so that's worth considering.

 

[Dibbs]

Noise is probably a little louder in a pistol, but not enough percievable difference if niether are surpressed.

In theory, more powder burns, inside the longer barrel of the carbine. Therefore, the blast is less, and the noise should be somewhat abated. But I don't notice much of a difference , in noise, between my 92FS, with a 4.7" barrel, and the CX4 carbine, with a 16.6" barrel.

 

[denton]

All the powder is burned well before the bullet exits, whether from a handgun or a rifle. We see muzzle flash because the propellant gas is hot enough to glow, and because it contains unburned hydrogen which ignites on contact with the oxygen in the air.

 

[John_R]

Download a decibel measuring app to your phone and take the two guns to the range.

Place the phone in your shirt pocket and record five shots with each gun, then record five shots with the phone on a table to the side.

Report the results.

/thread.

 

[chicharrones]

Download a decibel measuring app to your phone and take the two guns to the range.

Place the phone in your shirt pocket and record five shots with each gun, then record five shots with the phone on a table to the side.

Report the results.

/thread.

Yeah, I've tried that in the past. In my experience, a smart phone microphone and its internal technology can't react quickly enough for gun shot decibel readings. Same goes for my low end hand held decibel meter. They both work fine for sustained sound readings, though.

Of course, if smart phone tech has improved enough to work better than my experiences, that would be a great thing.

 

[mavracer]

The other interesting fact is that the longer barreled Beretta's breech is much closer to my ears when in a firing position than a pistol's breech is when held at arms length. That might not mean much in a manually operated gun, but in autoloaders . . .

Port pop is absolutely something to keep in mind.
After watching 100s of videos of suppressor testing I have no doubt that the noise from the port may be louder at the ear than from the muzzle of a 16" 9mm.

 

[Orion8472]

I am glad I brought this topic up. Very interesting discussion going on here!

Because I have sensitive hearing, and 9mm blast is [IMO] about at the limit I like to be exposed to [even with ear plugs and ear muffs], I may have to give up on 9mm completely [and my AR-15 for that matter] and just stick with 22lr......and the 38 Special out of my 1873 lever rifle. Shooting guns isn't my life, and if I can only do those types of firearms, I would be fine.

All of this is due to not being able to find much better hearing protection than I have. That being, foam ear plugs, and Howard Leight L3 ear muffs.

 

[chicharrones]

Thanks for all the replies.

I was just wondering if, with 9mm, it's the same as it is with 22lr. I have a 22lr pistol that is definitely louder than my 22lr rifles. And I have fired 38 Special out of a top load 1851 revolver and it was FAR louder to me than the same load out of my 1873 Taylors with 20" barrel.

So, I would hoping that a PC Carbine, with the 16" barrel, would be enough of a difference to where I could still keep the 9mm I have when I get rid of my pistols.

BTW, I really compare shooting my two PCCs with rifles firing rifle cartridges. My 16" barreled CX4 (9mm) and 16" barreled Marlin (.357) are certainly quieter than my my 16" barreled AR (5.56) and my 17.25" barreled GSR (.308). Which means the PCCs bridge the gap between rimfire and centerfire rifle cartridges very nicely in sound production. IMO, of course.

 

[denton]

The dB meter in your phone does not have enough dynamic range to measure muzzle blast.

 

[mavracer]

Because I have sensitive hearing, and 9mm blast is [IMO] about at the limit I like to be exposed to [even with ear plugs and ear muffs], I may have to give up on 9mm completely [and my AR-15 for that matter] and just stick with 22lr......and the 38 Special out of my 1873 lever rifle. Shooting guns isn't my life, and if I can only do those types of firearms, I would be fine.

Yep that's some sensitive hearing alright, have you thought about a suppressor a dead air wolfman would work on 9mm and a 5.56 rifle.
Warning though they are addictive.

 

[shoobe01]

...Another factor in pistol carbines and perceived noise is action timing. Direct blowback auto loaders will open the action earlier then a cam'ed or locked breech auto pistol...

Excellent point, as +/- all the current PCCs are straight blowback so not apples to apples. The carbine is theoretically sending at all to the side away from the shooter but it's pretty close so I'll bet it has some impact, as well as certainly being a bit harder to measure or just anecdotally observe, because the directionality.

I've also reminded of some discussion decades back about perceived recoil partly being driven by sound pressure at the shooter and therefore worse performance for a lot of people with draught blowback 380s over locked breech mid- and large-caliber guns

 

[Orion8472]

mavracer, I don't really want to jump through the government background check and $200 tax stamp hoop.....wait the how ever long period of time, spend the several hundred on a suppressor, just so I can shoot 9mm. It's unfortunate that suppressors require so much when it would be a huge benefit to people. I do appreciate the advice!

 

[CapnMac]

would be a huge benefit to people

Couple of possible steps to take, while we are at this,
Consider using subsonic ammo in both 9x19 and 5.56nato (ok, you may have to wait a moth or so for the supplies to build back up). Decreasing that whipcrack of the bullet is significant. And the projectiles still have 950-1000 fps on them to retain effectiveness.

The other issue would be to upgrade your earplugs for going under the muffs. The custom moulded ones are not that terrible expensive. (If you are doubling, I'd not get two sets of "electronic"--just too many variables to get both set to Goldilocks; so use one or the other.)

There's a 2(A) item--get out of indoor ranges, as they are horrible places for people with sensitive hearing.

Perception of gunshots has three components. Muzzle blast; sound impulse; and distance. Perception at 10m is much different than at 1m. The .44mag is a loud beast. The 5.56nato actually has a great impulse for the MV being above Mach 2.

 

[Hugger-4641]

Ok, this thread prompted me to do a little testing:
I downloaded a decibel meter app to my phone, problem is it was limited to 100db, so I couldn't use it close to the weapon. So I put the phone just inside the picture window of my living room while I went out on the front porch, about 10 feet away with the barrel at a 45% angle.
My grand daughter was watching Snow White in the next room and my wife was cooking lunch in the kitchen, so the ambient noise in the house was between 50 and 60db.
All of the 9mm were Blazer Brass 115gr RN.
I had my daughter write down the readings as I fired the following just for the fun of it:

PCC 9mm - 63db
M9A3 - 57db
STR-9 - 62db
CPX-2 - 78db
G-19 - 64db
XD-40 - 71db (165gr FN Blazer aluminum)
Taurus .357 - 66db (158gr HP Blazer Brass)
.25 acp - did not even register above ambient
.22/25 lite- 62db (winchester 36gr hp)
10/22 carbine- did not register above ambient. (Winchester 36g hp)
.32 acp - 69db

I'm not 100% convinced about the performance of my phone mic or the app because my daughter said the .357 was the loudest of them all to her and it seemed that way to me also. But it is interesting to see some data to support that there really isn't a significant difference between the carbine and the pistols.

 

[mavracer]

mavracer, I don't really want to jump through the government background check and $200 tax stamp hoop.....wait the how ever long period of time, spend the several hundred on a suppressor, just so I can shoot 9mm. It's unfortunate that suppressors require so much when it would be a huge benefit to people. I do appreciate the advice!

Understandable, another suggestion would be a linear compensator or shrouded brake they help some to direct noise away.
I've used levang style linears on 5.56, 308 and 22 they help some. I also switched out a tank style brake off my 450 bushmaster to a Witt SME shrouded brake went from obnoxious to very tolerable with just plugs for me.

 

[mjsdwash]

to all the people saying its perceptively and not actually louder due to distance from you ear, I'm going to point out the obvious:

You hold a handgun with your arms outstretched, vs a rifle shouldered. Just measuring, the muzzle of my 1911 is about 31" from my ear when firing normally, while my 16" rifle is about 27", so the rifle is actually closer. The rifle also has a muzzle break, and the rifle is still considerably quieter.

 

[Orion8472]

mavracer, I do have a linear comp. The Kaw Valley Mach 3. It works fairly well and I noticed that it does remove a bit of the blast. I could just continue to use that...but I do notice a bit of "blow back"? When I fired, one time, I felt something small hit just above my lip. It didn't really hurt, but felt it.

I have also used 147gr Federal and didn't really notice much of a difference over the 115gr I shot before them.